3 fly ash, slag, silica fume, and natural pozzolans
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Transcript of 3 fly ash, slag, silica fume, and natural pozzolans
Fly Ash, Slag, Silica Fume, and Natural Pozzolans
ByProf. Adel El Kordi
&Dr. Meheddene Machaka
Structural EngineeringDepartment
Faculty of EngineeringBeirut Arab University
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CVLE 321
Fly Ash, Slag, Silica Fume, and Natural Pozzolans
Also known as —SupplementaryCementing Materials (SCMs)— a material that, when used in conjunctionwith Portland cement, contributes to theproperties of the hardened concrete throughhydraulic or pozzolanic activity, or both.
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Supplementary Cementitious Materials (SCMs)
From left to right: Fly ash (Class C) Metakaolin (calcined clay) Silica fume Fly ash (Class F) Slag Calcined shale
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Supplementary Cementing Materials - Pozzolans
Pozzolan — a siliceous or alumino-siliceousmaterial that, in a finely divided form and inthe presence of moisture, chemically reactswith calcium hydroxide released by thehydration of portland cement to formcompounds possessing cementingproperties.
Natural Pozzolans — a natural materialwhich may also be calcined and/orprocessed ( eg. metakaolin, rice husk,volcanic ash, calcined shale)
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Specification and Class of Natural Pozzolans
Class N—Raw or calcinednatural pozzolans including: Diatomaceous earths Opaline cherts and shales Tuffs and volcanic ashes or
pumicites Calcined clays, including
metakaolin, and shales
ASTM C 618 (AASHTO M 295)
Metakaolin
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SEM Micrograph of Calcined Clay Particles
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SEM Micrograph of Calcined Shale Particles
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Specifications and Classes of Fly Ash
Class F—Fly ash withpozzolanic properties
Class C—Fly ash withpozzolanic and cementitiousproperties
ASTM C 618 (AASHTO M 295)
Fly Ash
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SEM Micrograph of Fly Ash Particles
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Specifications and Grade of Ground Granulated Iron Blast-Furnace Slags
Grade 80Slags with a low activityindex
Grade 100Slags with a moderateactivity index
Grade 120Slags with a high activityindex
ASTM C 989 (AASHTO M 302)
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SEM Micrograph of Slag Particles
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Applications forFly ash, Slag,Calcined Clay orCalcined Shale
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Specification for Silica Fume
ASTM C 1240Silica Fume—finely dividedresidue resulting from theproduction of silicon, ferro-silicon,or other silicon-containing alloysthat is carried from the burningsurface area of an electric-arcfurnace by exhaust gases.
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SEM Micrograph of Silica Fume Particles
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Applications for Silica Fume and Metakaolin
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Chemical Analysis of Typical Fly Ash, Slag, Silica Fume,Calcined Clay, Calcined Shale, and Metakaolin
Class Ffly ash
Class Cfly ash
Ground slag
Silicafume
Calcinedclay
Calcinedshale
Meta-kaolin
SiO2, % 52 35 35 90 58 50 53
Al2O3, % 23 18 12 0.4 29 20 43
Fe2O3, % 11 6 1 0.4 4 8 0.5
CaO, % 5 21 40 1.6 1 8 0.1
SO3, % 0.8 4.1 9 0.4 0.5 0.4 0.1
Na2O, % 1.0 5.8 0.3 0.5 0.2 — 0.05
K2O, % 2.0 0.7 0.4 2.2 2 — 0.4
Total Naeq. alk, % 2.2 6.3 0.6 1.9 1.5 — 0.316
Selected Properties of Typical Fly Ash, Slag, Silica Fume,Calcined Clay, Calcined Shale, and Metakaolin
Class Ffly ash
Class Cfly ash
Groundslag
Silicafume
Calcinedclay
Calcinedshale
Meta-kaolin
Loss on ignition,% 2.8 0.5 1.0 3.0 1.5 3.0 0.7
Blaine fineness,m2/kg 420 420 400 20,000 990 730 19,000
Relativedensity 2.38 2.65 2.94 2.40 2.50 2.63 2.50
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Typical Amounts of SCM in Concreteby Mass of Cementing Materials Fly ash
Class C 15% to 40% Class F 15% to 20%
Slag 30% to 45% Silica fume 5% to 10% Calcined clay 15% to 35%
Metakaolin 10% Calcined shale 15% to 35%
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Effect of Fly Ash on Mixing Water Requirements
Class offly ash
Fly ash content, % bymass of cementing
material
Change in mixing waterrequirement compared
to control, %C 25 -7F 25 -5C 50 -15F 50 -10
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Effect of Fly Ash on Bleeding of Concrete
Fly ash mixturesBleeding
Percent mL/cm2
Average of: Class CClass F
0.34 0.0111.31 0.044
Control mixture 1.75 0.059
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Effect of Fly Ash on Air-Entraining AdmixtureDosage and Air Retention
Fly ashmixtures
Percent of air-entraining admixture
relative to control
Air content, %Minutes after initial
mixing0 30 60 90
C 152 6.5 6.0 5.8 5.8F 299 6.3 5.3 4.7 4.5
Control mixture 100 6.6 6.0 5.6 5.3
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Effect of Slag on Heat of Hydration
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Effect of Fly Ash on Setting Time of Concrete
Fly ash test mixturesSetting time,
hr:min
Retardationrelative to
control, hr:minInitial Final Initial Final
Average of: Class C 4:40 6:15 0:30 0:45Class F 4:50 6:45 0:35 1:15
Control mixture 4:15 5:30 — —
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Effects of Supplementary Cementing Materialson Freshly Mixed Concrete
Reduced No/Little EffectFly ash Slag Silica
fumeNat.
PozzolansIncreased Varies
Water RequirementsWorkabilityBleeding and SegregationAir ContentHeat of HydrationSetting TimeFinishabilityPumpabilityPlastic Shrinkage Cracking 24
Compressive Strength Development
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Long Term Strength Development
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Cold Weather Strength Development
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Abrasion Resistance Vs. Compressive Strength
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Fly ash Calcined shale Slag Portland cement
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Frost Resistance of Fly Ash Concrete
Fly ash mixtures
Results at 300 cyclesFrost resistance in water,
ASTM C 666 Method A (AASHTO T 161)Expansion, % Mass loss, % Durability factor
Average of: Class C 0.006 1.6 101Class F 0.004 1.8 102
Control mixture 0.002 2.5 101
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Deicer-Scaling Resistance of Fly AshConcrete
Results at 300 cycles
Deicer scaling resistance,ASTM C 672
Water cure Curingcompound
Average of: Class CClass F
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Control mixture 2 2 31
Scaling Resistance Vs. W/C-Ratio
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Deicer-Scaling of Fly Ash Concrete (25% Replacement)
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Deicer-Scaling of Fly Ash Concrete (50% Replacement)
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Effect of Fly Ash and Slag on Alkali-Silica Reactivity
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Reduction of ASR by Calcined Clay and CalcinedShale
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Effects of Supplementary Cementing Materials on Hardened Concrete
Reduced No/Little EffectFly ash Slag Silica
fumeNat.
PozzolansIncreased Varies
Strength GainAbrasion ResistanceFreeze-Thaw and Deicer-Scaling ResistanceDrying Shrinkage and CreepPermeabilityAlkali-Silica ReactivityChemical ResistanceCarbonationConcrete Color 37